In case of a complexly fractured or pathologically destructed bone the restoration or preservation of the original functional shape is an indispensable prerequisite for its physiological regeneration. In this connection metal implants bridging the defect by a screw fixation of the non-injured bone sections or bone stumps to withstand the strain caused by muscle and tendon tension including necessary physiotherapeutic exercises have been used for more than six decades and are still increasingly used. This measure of bone surgery is referred to as “exercise-stable osteosynthesis”.
The shape preservation of the defect tubular bone against the physiological axial pressure is achieved by the implantation of a metal tube securing the bone fragments against a twist (torsion) by means of transverse screw fixations at its distal and proximal ends into the marrow cavity of the long bone between the joints. The main area of application of the intermedullary nail also referred to as Küntscher nail after its inventor, the surgeon Gerhard Küntscher, are the lesions in the central third of the long bones (Tibia, Femur and Humerus).
For the stabilisation of juxta-articular, particularly multi-fragmental lesions the intermedullary nail is unsuitable. In these cases the reconstruction of the shape is attempted by a screw fixation of the bone and its fragments by means of support plates of corrosion resistant steel or alloys such as Co, Cr, Mo and titanium alloys attached to their outer surface. The bone anchoring implants may be provided with bio-compatible coatings such as titanium niobium oxinitrite which have a high electric conductivity. In contrast to the intermedullary nail strained by axial pressures the support plate screwed transversely to the long bone axis is mainly stressed by flexion. Its supporting effect therefore depends on and is limited by its fatigue strength. The problem of the support plate osteosynthesis is therefore as follows: In case of given material- and shape-related properties the support plate and its screw fixation on the bone are required to win the race between bone healing and the breakage of the implant with the timely load-stable consolidation of the bone before the elasticity of the support metal comes to an end.
Another complication of bone healing connected to the implantation of foreign body implants of a larger volume is bacterial infection. It develops with the permanent displacement of blood vessels in the bone skin (periosteum) and in the usually thin soft tissue jacket around the implant. With the increasing resistance of certain germs (staphylococcus aureus) to antibiotics a central medicinal problem arises which can frequently only be “solved” by amputation, for example, in the area of the lower limbs. Statistical figures indicate an amputation rate of up to 10% in the area of the distal tibia and the foot. It has been shown for more than three decades in abiological situations in the orthopaedic and trauma surgical clinic that this disastrous trend can be avoided by using the method by Magnetodyn. In recent times, particularly in the past three to four years, the bactericidal effect and the activation of the antibiosis in case of resistant germs achieved by the application of the electromagnetic fields of the method by Magnetodyn could be successfully proved in vitro in fundamental experiments whereby the achievements in case of chronically infected bone defects documented in the clinic could be explained.
The utilisation of implanted bone support plates and bone screws as alternating current electrodes using their contact to the outputs of a secondary coil, the so-called carriers, was already described in the DT 1 918 299.
According to the DT 26 11 744 A1 the technology of the magneto-dynamically induced electro-osteostimulation of the method by Magnetodyn was integrated into the shaft and socket of hip prostheses.
The electro-intermedullary nail including a secondary coil and electrodes in the hollow cylinder of an intermedullary nail was described in the DE 26 36 818.
The DE 199 28 449 C1 relates to the integration of the secondary coil into the axial bore of a bone screw electrically contacting the shaft of the screw and a tip insulated with respect to the shaft. This system is, in practice, referred to as bipolar induction screw system (BISS). The bipolar induction screw as a solitary implant was limited to screw lengths of 75 to 110 mm. In the surgical clinic it is used for the magnetically induced electro-osteostimulation, for example in case of an osteonecrosis of the femoral head or in case of fractures of the femoral neck.